1. Field of the Invention
The present invention relates to a thin-film capacitor and a manufacturing method of the thin-film capacitor, in particular, to a thin-film capacitor which is disposed over a substrate in which an electronic circuit is formed and which has an improved high-frequency property and a manufacturing method of the thin-film capacitor. This is a counterpart of and claims priority to Japanese Patent Application No. 2004-256218 filed on Sep. 2, 2004, which is herein incorporated by reference.
2. Description of the Related Art
Along with demands for miniaturization, higher performance and high frequency of electronics devices in recent years, research and development of miniaturization and higher performance have been prompted with respect to electronic components mounted in the electronic devices. In particular, there is the necessity of disposing a lot more of the electronic components in a limited region in order to realize the higher performance. In general, the electronic components are mounted on a substrate. The electronic devices include integrated circuit devices. The integrated circuit devices are mounted on a printed circuit board and are sealed by resin. Alternatively, the integrated circuit devices may be mounted on the printed circuit board substantially without being sealed by the resin. The integrated circuit devices include many circuits which have various functions realized by combining a plurality of electronic elements such as transistors. The electronic elements include capacitors. Meanwhile, along with the above-described demands for the miniaturization, the higher performance and the high frequency of the electronics devices, there is the necessity of reducing size and thickness of the integrated circuit devices and mounting the integrated circuit devices which have the high performance and improved high-frequency properties. That is, it is desired that the size and the thickness of the integrated circuit devices are further reduced while the number of the integrated circuit devices is increased and structures of the integrated circuit device are made multilayered, in order to realize the miniaturization, the higher performance and the high frequency of the integrated circuit devices. The capacitors, which are used for the electronic devices with the above-described demands fulfilled, include thin-film capacitors. The thin-film capacitor includes a lower electrode film disposed over the substrate, a high dielectric film and an upper electrode film which are stacked.
Since the thin-film capacitor has the above-described laminated structure, film separation may occur due to a stress of each film in the thin-film capacitor, depending on the sizes of each of the lower electrode film, the high dielectric film and the upper electrode film. In order to ensure adhesiveness between the films in the thin-film capacitor, an adhesive film has been disposed between the films, or one high-capacity capacitor has been configured by a plurality of small-sized capacitors coupled in parallel to each other through aluminum wirings. However, since the one high-capacity capacitor has high resistivity due to resistances in the aluminum wirings, the high-frequency property of the capacitor might deteriorate. Furthermore, another thin-film capacitor is described in a Patent document 1 (Japanese Patent Publication Laid-open No. Hei 10-189389). The thin-film capacitor described in the Patent document 1 includes a first electrode film disposed on a substrate, a high dielectric film disposed on the first electrode film and a second electrode film disposed on the high dielectric film. That is, the high dielectric film is disposed between the first and second electrode films. Also, the first and second electrode films of the thin-film capacitor described in the Patent Document 1 respectively include a plurality of slit portions which intersect with each other at a predetermined relative angle, in order to reduce inductance in the thin-film capacitor. When the first electrode film described in the Patent Document 1 includes the slit portions, adhesiveness may be improved between the first electrode film and the high dielectric film or between the first electrode film and an insulating film disposed under the first electrode film, to some extent.
However, in the thin-film capacitor as described in the Patent Document 1, all of the slit portions are arranged from one side (i.e., from two sides of the first rectangular electrode film which cross each other at right angles) toward the other side (other two sides which face the above-described two sides). Therefore, electrical current may not flow smoothly in regions between the slit portions of the first electrode film. As a result, the resistivity of the first electrode film increases, and then the high-frequency property of the thin-film capacitor may deteriorate. In addition, similar phenomena may occur in the second electrode film. That is, the thin-film capacitor as described in the Patent Document 1 has limitations to improve the high-frequency property.
Furthermore, each end of the slit portions of the thin-film capacitor has a sharp angle at a central side of the first electrode film. Therefore, during the manufacturing processes of the thin-film capacitor, a void filled with gas may occur at each end of the slit portions. When the gas in the voids expand by heat treatment during the manufacturing processes, film separation may occur between the first electrode film and the insulating film or between the first electrode film and the high dielectric film. Likewise, film separation may occur between the second electrode film and the high dielectric film. That is, the thin-film capacitor as described in the Patent Document 1 has difficulty improving the adhesiveness in the first electrode film, the high dielectric film and the second electrode film.